Method for detecting impurities in an oil sample

ABSTRACT

A chemical test kit and method for detecting the presence of impurities in an oil sample is provided. The test kit is comprised of two flexible translucent or transparent containers, each with at least one breakable capsule mounted within it. One of the flexible containers has a means for separating an aqueous layer from an oil layer. The capsules contain reagents capable of extracting the impurity to be detected from the oil into an aqueous layer and indicating the presence of a threshold concentration of the impurity. The method involves the steps of introducing an oil sample into a first flexible container, breaking the capsule within it by squeezing the flexible container in the vicinity of the capsule, transferring the aqueous layer to the second container, and breaking the capsule within the second container in the same manner. A chemical reaction occurs in the second container indicating whether the impurity is present at a given threshold concentration.

The present invention is directed to a chemical test kit and method tobe used in the field for determining the presence of threshold amountsof impurities in an oil sample. Specifically, the present invention isdirected to a chemical test kit and method to be used in the field fordetermining the presence of threshold amounts of polychlorinatedbiphenyl in transformer oil.

A method and testing container for detecting the presence of certaincomponents or substances in biological fluids is disclosed in U.S. Pat.No. 3,036,894. The testing container has a flexible tubular body withnon-communicating individual compartments, some of which containreagents, which allow for transfer of the contents of the precedingcompartment to a succeeding compartment. The substance to be tested ispassed sequentially through each compartment and intermixed with thesubstances contained therein until it reaches the final compartmentwhere the tested substance can be removed for test reading andconclusion.

A small testing tube for the chemical analysis of gas compositions isdisclosed in U.S. Pat. No. 3,022,141. The testing tube disclosed thereincontains three or more separately arranged reagents or layers ofreagents, one or more reagents are placed in one or more breakableampoules. The testing tubes are breakable in the area of the ampoulesbut are provided with a flexible reinforcing coating. The gas flowsthrough the testing tube contacting each reagent in sequence and finallyreaches the indicator layer where the presence of the particularcomponent is detected. Both ends of the testing tube are sealed and arebroken just prior to testing.

Another method for measuring gas, vapor and aerosol components in an airsample using a glass testing tube is disclosed in U.S. Pat. No.4,300,910. The disclosed testing tube has a breakable tip at each endand contains a breakable ampoule, an entraining filter, a reactionlayer, an empty tube chamber and a liquid lock in that order. As the gaspasses through the testing tube, the particles are entrained by thefilter. The ampoule is broken to direct a solvent through the filter todissolve the materials and to pass them into a reaction layer where acolor reaction takes place. The color reaction is visible in the emptychamber and indicates which components are present in the air sample.

There is a need for a simple chemical test method and kit which can beused in the field by a relatively untrained person to determine whetherthe oil in a transformer has been contaminated with polychlorinatedbiphenyl [hereinafter sometimes referred to as PCB] in excess of theEnvironmental Protection Agency regulations. There are currently anestimated 20,000,000 transformers which will have to be analyzed forpolychlorinated biphenyl contamination in order to comply with thecurrent regulations. Many of these units are PCB-free, that is, theycontain less than 50 ppm of PCB's. The method and chemical test kit ofthe present invention could eliminate the necessity of costly laboratoryanalysis on about 60% of these transformers.

In general, it is an object of the present invention to provide a novel,simple, reliable, and routine chemical test kit and method for use inthe field to determine the presence of impurities in an oil sample.

Specifically, it is an object of the invention to provide a novel,simple, reliable, and routine chemical test method and kit for use inthe field to determine whether the polychlorinated biphenyl content intransformer oil is close enough to the Environmental Protection Agencyregulation limit to require more accurate laboratory analysis.

Another object is to provide a chemical test method which can beperformed by someone with no chemical training.

Another object of the invention is to provide a chemical test kit andmethod which will in some cases eliminate the necessity of costlylaboratory analysis.

Another object is to provide an inexpensive disposable chemical testkit.

In general, the present invention provides a chemical test kit and amethod for detecting the presence of certain impurities in an oilsample. The chemical test kit comprises two flexible containers, eachwith at least one breakable capsule mounted within it. The firstcontainer has a capsule containing a reagent capable of reacting withthe impurity to be detected and extracting the impurity from the oilinto an aqueous layer. The first container also has a means forseparating the aqueous layer from the oil layer, preferably a cap with anozzle which can be opened to pour the second aqueous layer from thecontainer. The second container has a capsule containing a reagent whichis capable of visibly reacting with the impurity to be detected,indicating the presence of that impurity at a certain thresholdconcentration.

The particular reagent contained in each capsule, and the precise amountand concentration of each reagent, will be determined based upon whichimpurity is to be detected in the oil sample, and premeasured quantitiesof each reagent will be pre-packaged in the capsules of the chemicaltest kit.

The method involves the steps of introducing an oil sample into a firstflexible container, breaking a capsule in the first container, shakingthe container, and after the aqueous layer has formed, separating theaqueous layer from the oil layer by transferring the aqueous layer intoa second flexible container, breaking a capsule in the second container,and shaking the container, the color of the solution will indicate thepresence of the impurity at a threshold concentration.

Various types of analysis may be performed with the chemical test kitand method of the present invention, for instance, the kit can beequipped to determine the presence of impurities in oil samples, such aspesticides and/or degreasing materials, inhibitors, dissolved gases,acids, and polychlorinated biphenyl.

Additional objects and features of the invention will appear from thefollowing description in which the preferred embodiments have been setforth in detail in conjunction with the accompanying drawings.

FIG. 1 is a side elevational view schematically illustrating the firstcontainer of a preferred embodiment of the chemical test kit of thepresent invention.

FIG. 2 is a side elevational view schematically illustrating the secondcontainer of a preferred embodiment of the chemical test kit of thepresent invention.

FIG. 3 is a side elevational view schematically illustrating a preferredembodiment of the chemical test kit in operation.

Referring to FIGS. 1 and 2, a preferred embodiment of the chemical testkit of the present invention is illustrated. The chemical test kit iscomprised of two flexible transparent or translucent containers. FIG. 1represents a first flexible transparent container in which the impurityto be detected is extracted from the oil into an aqueous layer. FIG. 2represents a second flexible transparent container in which a chemicalreaction takes place, indicating by the color of the solution, thepresence of the impurity to be detected at a threshold concentration.

Referring to FIG. 1, the container 11 is comprised of a flexibletransparent material, preferably polypropylene or polyethylene. Thecontainer has at least one breakable capsule 12 mounted within it andcontaining a chemical reagent. In certain applications, two chemicalreagents may be necessary to perform the desired reaction and thus twobreakable capsules 12 and 13 would be mounted within the container 11 asshown in FIG. 1. The container in FIG. 1 also has a cap 14 with a nozzle15 shown in the open position by solid lines and in the closed positionby broken lines.

Referring to FIG. 2, the second container of the chemical test kit,container 21, is also comprised of a flexible transparent material,preferably polypropylene or polyethylene. There is at least onebreakable capsule 22 mounted within container 21 containing a reagentwhich will indicate the presence of the impurity to be detected. Incertain applications, two reagents may be necessary to perform thedesired chemical reaction, thus two breakable capsules 22 and 23 will bemounted within the container 21. A cap 24 is also provided.

The method of detecting the presence of certain substances in an oilsample using the chemical test kit of the present invention involvesremoving cap 14 from container 11, introducing an oil sample intocontainer 11, and replacing cap 14 with nozzle 15 in the closedposition. If there is more than one encapsulated reagent, the capsulesare broken in sequence depending upon which reagent must react firstwith the impurity to be detected. Assuming that two reagents arerequired in the particular application, the operator will break thefirst capsule 12, preferably by squeezing the flexible container in thevicinity of the capsule, shake container 11, break the second capsule 13in the same manner, shake container 11 and allow the chemical reactionsto take place. One of the reagents encapsulated should be in an aqueoussolution or at some point an aqueous solution should be introduced intocontainer 11 to allow the substance to be extracted from the oil into anaqueous layer.

For those applications where the oil chemically interferes with thedesired reaction, after the two layers have been formed the container 11should be inverted so that the aqueous layer 16 forms in the end nearthe cap 14 as shown in FIG. 3. Cap 24 is then removed from the secondcontainer 21. The nozzle 15 on cap 14 of container 11 is then opened andthe aqueous layer 16 in container 11 flows into the second container 21.The nozzle should be closed before the oil layer begins to enter thesecond container. At this point, cap 24 can be replaced and the operatorcan break the first capsule 22, preferably by squeezing the flexiblecontainer in the vicinity of the capsule, shake the container, break thesecond capsule 23 in the same manner, if a second capsule is present,and shake the container. At this point a chemical reaction will takeplace visibly indicating to the operator whether the substance to bedetected is present at the threshold concentration.

In some applications, the oil may not chemically interfere with theindicating reaction and it will not be necessary to separate the aqueouslayer from the oil layer prior to initiating the indicating reaction. Insuch cases, all necessary reagents can be encapsulated in one flexibletranslucent or transparent container, and the test to determine theprescence of the impurities can be conducted in a single container. Theparticular reagent, the number of encapsulated reagents, and the amountand concentration of each reagent will vary depending upon whichsubstance is being detected.

When the chemical test kit of the present invention is to be used fordetermining the presence of polychlorinated biphenyl in transformer oil,the capsules in the kit will contain reagents necessary to strip thechlorine from the polychlorinated biphenyl molecule and to detect thepresence of a threshold concentration of the chloride ion thus formed.

A number of technqiues using metallic sodium or lithium and suitablesolvents for stripping the chlorine from the polychlorinated biphenylmolecule are known. The chlorine is converted to sodium or lithiumchloride. The amount of chloride formed is an indirect measure of thePCB originally present. In the presence of water, sodium or lithiumchloride produces chloride ions which are easily measurable in minuteconcentrations using a dye indicator with a mercury titrant.

Referring to FIG. 1, when the kit is to be used to detect the presenceof polychlorinated biphenyl, the first container 11 will contain atleast one breakable capsule 12 containing an alkali metal, such assodium or lithium. When an oil sample is introduced into container 11and capsule 12 is broken releasing the alkali metal, a chemical reactionbegins in which the chlorine atoms on the polychlorinated biphenylmolecule are stripped from the carbon in the biphenyl molecule. Thechlorine is replaced by hydrogen atoms removed from other molecules orthe biphenyl residue couples with other biphenyl molecules. When all thechlorines have been replaced by hydrogen, the polychlorinated biphenylis converted to biphenyl. The chlorine molecules form an alkalichloride, such as sodium chloride or lithium chloride. The reactionoccurs with finely-dispersed alkali metal, but the rate of the processcan be increased greatly if the reactive alkali metal is distributed ona molecular basis. Thus, the preferable reagent for capsule 12 is anorgano-alkali salt, such as organo-sodium salt or organo-lithium salt.

Metallic sodium is a preferred alkali metal reagent for the presentinvention. Metallic sodium reacts with small aromatic hydrocarbonmolecules, such as those containing up to twenty carbon atoms, to formorgano-sodium salts. These salts can then dissolve in oil and react withthe polychlorinated biphenyl to form biphenyl and sodium chloride. Thearomatic hydrocarbon reverts to its original form. In order to build upquantities which will give attractive PCB conversion rates, theoragno-metallic salt must be stabilized by the presence of additionalmolecules, known as ligands. The ligands serve to solvate the sodiumsalt and increase its stability. A preferred aromatic hydrocarbon toform a sodium salt is naphthalene and a preferred stabilizing ligand canbe selected from the group consisting of tetrahydrofuran and diethyleneglycol dimethyl ether. The preferred stabilizing ligand according to thepresent invention is diethylene glycol dimethyl ether.

If lithium is used as the alkali metal to strip chlorine frompolychlorinated biphenyl, a lithium salt can be formed by reactingmetallic lithium with the butane molecule yielding butyl lithium. Butyllithium would yield lithium chloride on reaction with polychlorinatedbiphenyl.

After the chlorine has been stripped from the polychlorinated biphenylin the oil sample in container 11, an aqueous solution should be addedto extract the chloride ions into an aqueous phase. An aqueous solutioncan be added to container 11 by removing cap 14 or a second capsulecontaining an aqueous solution can be mounted within container 11 andbroken after the conversion of polychlorinated biphenyl to chloride toextract the chloride into an aqueous layer.

A preferred embodiment of the present invention has two capsules mountedwithin container 11. The first capsule 12 contains the metallic sodiumdispersed in a light oil and the second capsule 13 contains naphthalene,an organo-metallic salt former, and diethylene glycol dimethyl ether, astabilizing ligand. An acid/buffer solution, such as an aqueous solutioncontaining nitric acid and disodium phosphate, is added to container 11after the necessary reactions have taken place to dechlorinate thepolychlorinated biphenyl in order to extract the chloride ions into anaqueous layer. The acid/buffer solution is contained in container 21 andis not encapsulated in a breakable capsule.

When the chemical test kit is being used to detect the presence of PCBin transformer oil, container 21 has at least two breakable capsules 22and 23 mounted within it. One capsule contains a mercury titrant and theother capsule contains a dye indicator. The amount of mercury titrantshould correspond to that required to react with all of the chlorideions in a threshold concentration of PCB. The current EnvironmentalProtection Agency regulation considers oil to be PCB-free if it containsless than 50 ppm of PCB. Therefore, the amounts and concentrations ofthe various reagents used in the kit will be chosen to differentiatebetween chlorides corresponding to less than or greater than 50 ppm ofPCB. When the threshold concentration of PCB is 50 ppm, a preferredmercury titrant is mercuric nitrate and a preferred dye indicator isdiphenyl carbazone or a mixture of diphenyl carbazone and bromphenylblue. The most preferred indicator for the present invention is diphenylcarbazone alone.

When the aqueous layer containing the chloride ions is added tocontainer 21 and the capsules 22 and 23 containing the mercuric titrantand the dye indicator are broken, the solution should assume one of twocolors which indicate whether the PCB content is more or less than athreshold concentration. When the dye indicator is diphenyl carbazone ordiphenyl carbazone and bromphenyl blue, the chloride ions react with themercuric ions in the titrant to form mercuric chloride while excessmercuric ions and the diphenyl carbazone dye indicator react to form ablue-violet color indicating a PCB content of less than 50 ppm. If theamount of chloride ions present is equivalent to a polychlorinatedbiphenyl content of greater than 50 ppm, there are no mercuric ions leftto react with the dye indicator, resulting in a colorless to yellowsolution.

The method for detecting the presence of polychlorinated biphenyl in anoil sample, utilizing the chemical test kit described above, involvesthe steps of: introducing an oil sample into the first container 11,replacing the cap 14, breaking capsule 12, preferably by squeezing theflexible container in the vicinity of capsule 12, thereby releasing thealkali metal, shaking the container 11 thereby initiating the chemicalreaction whereby the alkali metal strips the chlorine frompolychlorinated biphenyl to form an alkali chloride, adding abuffer/acid solution to container 11, shaking container 11 therebyextracting the alkali chloride into an aqueous layer, separating theaqueous layer from the oil layer by transferring the aqueous layerthrough a separating means 15 on container 11 into the second container21, breaking the first capsule 22 containing a mercury titrant in thesecond container 21, preferably by squeezing the flexible container inthe vicinity of capsule 22, thereby releasing the mercury titrant,shaking container 21, breaking the second capsule 23 containing a dyeindicator in the same manner, shaking container 21, and observing thecolor of the solution to determine whether the threshold concentrationof polychlorinated biphenyl is present in the oil sample.

The preferred method when the PCB content of 50 ppm is to be detectedinvolves breaking two capsules in container 11, the first containing anorgano-metallic salt former and a stabilizing ligand, preferablynaphthalene and diethylene glycol dimethyl ether, and the secondcontaining sodium dispersed in a light oil. Preferably, the acid/buffersolution is contained in container 21 and is poured into container 11after both capsules 12 and 13 have been broken and the chemical reactionhas taken place. This results in the extraction of the chloride ionsinto the aqueous layer and allows for subsequent separation of theaqueous layer from the oil layer by transferring the aqueous layer intocontainer 21. Preferably, the separation step involves invertingcontainer 11 with nozzle 15 in the closed position to allow the aqueouslayer to form adjacent to the cap and positioning container 21 undercontainer 11 so that when the nozzle 15 is opened the aqueous layer incontainer 11 is poured into container 21. The nozzle is closed when theaqueous layer is in container 21 so that the oil layer is retained incontainer 11. With the aqueous layer in container 21, the two capsules22 and 23 are broken and the indicating reaction can take place.Preferably, the first capsule contains mercuric nitrate and the secondcapsule contains biphenyl carbazone.

When the chemical test kit is used to determine the presence of morethan 50 ppm of PCB's in transformer oil, the preferred reagents,concentrations and number of capsules in each container are as follows.The first flexible container contains two capsules, one capsule contains200 μl of a 20% sodium dispersion in light oil, the second capsulecontains 200 μl of a 4:1 ratio of diethylene glycol dimethyl ether andnaphthalene; the second flexible container contains 7 ml. of abuffer/acid solution and two capsules, one capsule containing 1 ml. of0.0012 Molar mercuric nitrate, the second capsule containing 0.25 ml. of0.1% diphenyl carbazone. In order to achieve the desired end color foran oil sample containing more than 50 ppm of PCB's and/or less than 50ppm of PCB's, a 5 ml. oil sample should be tested.

EXAMPLE 1

Twelve mg. of sodium was placed in an empty 12 ml. polypropylene testtube. Two hundred μl of diethylene glycol dimethyl ether and 50 mg. ofnaphthalene were added to a 3 ml. sample of oil externally. Five ml. ofoil were then added to the test tube and the test tube was shaken. Fiveml. of water containing nitric acid, disodium phosphate buffer, anddiphenyl carbazone indicator were added to the tube and the tube wasagain shaken. Mercuric nitrate equivalent to 21 ppm of chloride was thenadded. The samples which originally contained 40 ppm of PCB's produced aviolet-blue color in the aqueous phase. The samples which contained 50ppm or more of PCB's resulted in no color change, a yellow colorpersisted.

What is claimed is:
 1. A method for detecting the presence ofpolychlorinated biphenyl at above a predetermined thresholdconcentration in an oil sample, comprising the steps of:(a) introducinga predetermined volume of an oil sample into a first flexible containerhaving at least two breakable capsules mounted therein, a first one ofsaid capsules in said first container containing a reagent comprisingnaphthalene and diethylene glycol dimethyl ether and a second one ofsaid capsules in said first container containing a reagent comprisingsodium, in amounts sufficient to completely convert a predeterminedthreshold amount of polychlorinated biphenyl, as established by saidpredetermined threshold concentration and said predetermined samplevolume, to chloride ions and biphenyl, said first container having meansfor separating an aqueous layer from an oil layer into a second flexiblecontainer; (b) breaking said capsule containing naphthalene anddiethylene glycol dimethyl ether in said first container; (c) thenshaking said first container; (d) breaking said capsule containingsodium in said first container; (e) then shaking said first container;(f) transferring a predetermined volume of an aqueous buffer/acidsolution contained in said second container to said first container; (g)then shaking said first container; (h) separating the resulting aqueouslayer from the resulting oil layer by transferring the aqueous layerthrough said separating means into said second container, said secondcontainer having at least two breakable capsules mounted therein, afirst one of said capsules in said second container containing a reagentcomprising mercuric nitrate and a second one of said capsules in saidsecond container containing a reagent comprising diphenyl carbazone,said mercuric nitrate and said diphenyl carbazone being present inamounts sufficient to cause a positive reaction if the concentration ofchlorides in said aqueous layer is greater than an amount correspondingto said predetermined threshold concentration of polychlorinatedbiphenyl; (i) breaking said capsule containing mercuric nitrate in saidsecond container; (j) then shaking said capsule containing diphenylcarbazone by shaking said second container; (k) breaking said capsulecontaining diphenyl carbazone in said second container; and (l) thenshaking said second container, a blue-violet color indicating thepresence of less than said predetermined threshold concentration ofpolychlorinated biphenyl and a colorless to yellow color indicating apositive reaction resulting from the presence of more than saidpredetermined threshold concentration of polychlorinated biphenyl insaid oil sample.
 2. A method according to claim 1 wherein saidseparating means comprises a cap with a nozzle contructed and arrangedto be selectively closed until step (h) and opened during the separationof step (h) and wherein said separation step comprises the steps ofinverting said first container to cause the aqueous layer to be formedadjacent to said cap, placing an inlet of said second container adjacentand in flow communication with said nozzle, opening said nozzle to causethe aqueous layer to flow into said second container, and closing saidnozzle after the aqueous layer has been transferred to said secondcontainer to cause the oil layer to remain in said first container.
 3. Amethod according to claim 1 wherein said first one of said capsules insaid first container contains about 200 μl of a 20% sodium dispersion ina light oil, wherein said second one of said capsules in said firstcontainer contains about 200 μl of a 4:1 ratio of diethylene glycoldimethyl ether and naphthalene, wherein said predetermined volume ofaqueous buffer/acid solution in said second container comprises about 7milliliters of said buffer/acid solution, wherein said first one of saidcapsules in said second container contains about 1 milliliter of 0.0012Molar mercuric nitrate, wherein said second one of said capsules in saidsecond container contains about 0.25 milliliters of 0.1% diphenylcarbazone, and wherein said predetermined volume of oil sample is about5 ml.